Search

High mobility channel materials like SiGe, Ge and IIIV receive lots of interest in order to enable the continuation of Moore’s path during the upcoming technology nodes. Recently Si-cap-free SiGe passivation with the number of interface states (NIT) down to 2 1011 cm-2 have been demonstrated. [1-3] A clear correlation was established between Ge-content in the SiGe-oxide and NIT. Unfortunately no process information has been provided on how the Ge-oxide-free interlayers were obtained. In a separate study the impact of HF, HCl and SC1 cleaning solution on the SiGe surface and oxide composition was reported. [4] A comparison of SiGe Gate-All-Around (GAA) and FinFET devices using a Si-cap-free SiGe 25% passivation scheme in a replacement metal gate (RMG) integration indicate the device performance is improved by a TMAH (aq) treatment prior to SiGe interlayer formation and high-k deposition. [5] Here the formation of a SiGe wet chemical oxide will be presented. The impact of dummy gate processing on the interlayer composition is reported. Also the impact of a TMAH (aq) treatment prior to chemical oxide formation has been analyzed and will be reported. Blanket strained SiGe 25% and 45% were grown by epitaxy. The SiGe-substrate and -oxide composition were measured by angle-resolved XPS using the Si2p and Ge3d peaks. The Ge3d peak is fitted with three different compounds: elemental Ge, GeO2 and Ge-suboxide. The angle dependence lets us estimate the distribution of the different components with respect to the sample top surface. An concentration increase with increasing angle (relative to the surface normal) indicates the compound is located closer to the sample surface. And reversely a concentration increase with increasing angle indicates the compound is located deeper into the sample. A native oxide was grown on SiGe 25 and 45% by exposing the wafers to the cleanroom air for approx. 1 week. The native oxide was found to be stoichiometric or nearly stoichiometric with a uniform Ge content throughout the oxide for SiGe 25 and 45% respectively. A wet chemical oxide was grown using an ‘imec clean’ [6] having a final O3/HCl (aq) rinse. The wet chemical oxide is Ge-poor compared to the SiGe substrate. No or only a small variation in Ge content of the SiGe-oxide is seen with ARXPS. However the fraction Ge-suboxide decreases with increasing angle, indicating the Ge-suboxide are located deeper within the sample, so closer to the SiGe-oxide/SiGe-substrate interface. The Ge-content of the SiGe-substrate after wet chemical oxidation shows a weak incident-angle-dependence, indicative a limited Ge enrichment of the SiGe substrate towards the SiGe-oxide/-substrate interface. The low Ge content of the SiGe-oxide is attributed to the water solubility of GeO2. The increase in Ge-content towards the SiGe-oxide/-substrate can be (at least partially) attributed to the poor water solubility of Ge-suboxide. The small increase in Ge content of the SiGe substrate can be attributed to the thermodynamically preferred oxidation of Si over Ge. The combined impact of dummy gate deposition, spike anneal and dummy gate removal prior to SiGe interlayer formation was investigated by AR-XPS and SIMS. The temperature used during spike anneal was found to have a significant impact on the Ge-content of the SiGe-oxide formed during an O3-last imec clean. The results will be reported in detail at the conference. The impact of TMAH (aq) on the chemical oxide composition and surface roughness will also be reported. TMAH (aq) was found to improve SiGe device performance. [5] Also the interaction with the subsequent HfO2 deposition will be reported. In summary SiGe is found to behave as a non-linear combination of Si and Ge. In HF-free aqueous solutions, the SiGe oxide composition is a combination of (1) thermodynamically preferred oxidation of Si versus Ge; (2) poor water-solubility of SiO2 and/or its low solubilization rate; and (3) fast dissolution of GeO2 but slow dissolution of Ge-suboxides. [1] CH Lee et al. VLSI 2016. [2] S. Siddiqui et al. presented MRS Spring Meeting 2016. [3] CH Lee et al. IEDM 2016. [4] S.L. Heslop et al. ECS Trans 69 (2015) 287. [5] H. Mertens et al VLSI 2015. [6] M. Meuris et al. Solid State Phenom, July 1995, p. 109. Figure 1

The increasing scientific and industry interest in 2D MX

Wear mechanisms including fracture and plastic deformation at the nanoscale are central to understand sliding contacts. Recently, the combination of tip-induced material erosion with the sensing capability of secondary imaging modes of AFM, has enabled a slice-and-view tomographic technique named AFM tomography or Scalpel SPM. However, the elusive laws governing nanoscale wear and the large quantity of atoms involved in the tip-sample contact, require a dedicated mesoscale description to understand and model the tip-induced material removal. Here, we study nanosized sliding contacts made of diamond in the regime whereby thousands of nm3 are removed. We explore the fundamentals of high-pressure tip-induced material removal for various materials. Changes in the load force are systematically combined with AFM and SEM to increase the understanding and the process controllability. The nonlinear variation of the removal rate with the load force is interpreted as a combination of two contact regimes each dominating in a particular force range. By using the gradual transition between the two regimes, (1) the experimental rate of material eroded on each tip passage is modeled, (2) a controllable removal rate below 5 nm/scan for all the materials is demonstrated, thus opening to future development of 3D tomographic AFM.

High vacuum scanning spreading resistance microscopy (HV‐SSRM) and electron holography (EH) methods are used to study two‐dimensional (2D) cross‐sectional doping profiles of low energy high dose ion implantations including conventional beam‐line 75As implant and AsH3 plasma doping (PLAD). Both methods show quantitative definition of junction depths xj in vertical and lateral directions, and have been demonstrated to be powerful techniques for 2D doping profiling study. It has been found that AsH3 PLAD with −10 kV voltage and 1×1016/cm2 dose shows slightly deeper junction depth xj, both of vertical xj(V) and lateral xj(L) and with slightly larger xj(L)/xj(V) ratio than beam‐line 75As implant with 10 keV energy and 8×1015/cm2 dose. Good correlations among 2D HV‐SSRM doping profiles, 2D EH doping profiles, 2D doping profile simulation, and 1D SIMS/ARXPS As profiles have been demonstrated. Very good correlation between 2D doping profiles and device parameters has been demonstrated.

We have directly measured two-dimensional (2-D) dopant profiles of millisecond-annealed p-MOSFETs by scanning spreading resistance microscopy (SSRM) for the first time. The measured 2-D dopant profiles agree with simulated dopant profiles obtained by using calibrated TCAD tools. Three-dimensional (3-D) SSRM simulation reveals that the current SSRM probe-contact radius has enough spatial resolution. For further scaling, however, smaller radius of probe is required.

The density of hafnium oxide films grown by atomic layer deposition for high-κ gate dielectric applications was investigated for films with thickness in the nanometer range. The density, measured by combining the film thickness from transmission electron microscopy with the amount of hafnium deposited from Rutherford backscattering, decreased with decreasing film thickness. The dielectric constant of hafnium oxide remained constant with decreasing film thickness, however. The main reason for the decrease in the measured density seemed not to be a decrease in the inherent material density. Instead, the relative importance of interface roughness in the density measurement increased with decreasing film thickness.

The use of Si based materials for optoelectronic applications is hampered by the indirect nature of the band gap. One possible solution by which to improve the radiative light emission is three-dimensional Stranski-Krastanow growth of Si1-xGex or pure Ge on top of Si. In this article we give a detailed overview about the growth kinetics observed for Ge growth in a standard production oriented chemical vapor deposition system. With increasing deposition time, we observed the usual changeover from monomodal to bimodal island distribution. The island morphology and density can be controlled by varying the growth conditions or by applying a thermal anneal after island growth. Island densities up to 2.3x10(10) cm(-2) have been obtained for depositions at 650 degreesC. A Si cap layer is needed for photoluminescence measurements as well as for some device structures. However, Si capping at 700 degreesC leads to nearly total dissolution of small islands and truncation of bigger dome-shaped islands. This can be prevented by reducing the deposition temperature and by changing the Si gas source. Photoluminescence measurements demonstrate the high layer quality of Si capped islands by the clear separation between the no-phonon line and the transversal optical (TO) replica and the high peak intensities. The spectral range of the island luminescence is between 1.35 (920 meV) and 1.50 mum (828 meV) and depends on the growth conditions. At 20 K, we found up to 70 times higher values for the integrated no-phonon and the TO luminescence from the islands, compared to the integrated intensity from the Si TO peak. Nevertheless, the high photoluminescence intensity can be further enhanced by a thermal treatment in a H-2 plasma. Clear island luminescence up to 200 K has been observed after such thermal treatment, which shows the potential of this material system for optoelectronic device applications. (C) 2001 American Institute of Physics.

In this work, we present the use of SSRM, an electrical characterization technique based on atomic resistance microscopy (AFM), as a verification tool for the accurate calibration of two dimensional (2D) process simulations on advanced high speed bipolar HBT devices with fT/fmax values exceeding 200GHz. The 2D HBT process simulator has been calibrated based on SIMS measurements and TEM pictures. The process simulations consider coupled diffusion of carbon and silicon point defects under several RTA conditions [1]. Kick-Out and Frank-Turnbull mechanisms model the carbon diffusion. Extended short-loop experiments under equilibrium and non-equilibrium conditions increased the accuracy of the simulations [2]. Lateral and vertical scaling of the bipolar device dimensions is an absolute requirement for obtaining current and power cutoff frequencies (fT, fmax) above 200GHz [3]. The state-of-the-art QSA HBT investigated in this work for instance has an enclosure of active area over the poly emitter of only 0.03μm. As the external base implantation, needed to obtain low base resistance, is done after the poly emitter patterning, a precise determination of the base collector junction becomes difficult but at the same time important, taking into account the interaction with the selectively implanted collector (SIC) and the importance of the base-collector junction location for the DC device characteristics. Simulations using the calibrated 2D-TCAD platform show the different shapes of the external base-collector metallurgical junction as a function of the poly emitter sidewall angle (fig 1). The vertical depth of the basecollector metallurgical junction along the STI drops from 90nm to 75nm and even 45nm for a poly emitter sidewall angle of respectively 90°, 80° and 73°. From crosssectional pictures we know that the poly emitter sidewall angle is around 80°, but so far we were unable to verify the exact position of the base-collector metallurgical junction on real silicon. A key advantage of the SSRM technique however is its capability to determine the precise location of electrical transistor junctions. The improvements in sample preparation and the introduction of full diamond probes have enabled a drastic increase of the spatial resolution down to 1-3nm [4,5], even for HBT transistors where many materials with different hardness are present (silicon, polysilicon, oxide, nitride, silicide, SiGe). Figures 2 and 3 show such SSRM plots for the QSA 0.13μm SiGe:C HBT. A comparison is shown with a 2DTCAD plot and with a TEM picture respectively. Geometrical distances and the base-collector junction can be clearly distinguished on the SSRM plots. A quantification of the key geometrical and electrical distances extracted from the SSRM data are summarized in table 1. They are compared with the TCAD values. SSRM quantifies correctly known geometrical values like for instance the nitride thickness of the emitter window and the oxide undercut under this nitride. The measured lateral and vertical electrical junction depths from SSRM correspond well with the values extracted from the calibrated 2D-TCAD platform. We conclude therefore that the 2D-TCAD process simulator is correctly calibrated. This TCAD platform will be used for future process optimization of advanced high speed HBT devices.

In order to reach the ITRS goals for future complementary metal-oxide semiconductor technologies there is a growing interest in using germanium as an alternative substrate material in view of its higher mobility. Different species and thermal budgets are presently being investigated in order to determine the most likely candidates for the required junction formation. A key issue is the accurate determination of the achievable electrical activation, i.e., the reliable measurement of the sheet resistance and electrical depth profile. In order to be applicable to Ge-based junctions, standard techniques such as the spreading resistance probe and scanning spreading resistance microscopy (SSRM) need to be reevaluated in terms of their performance and operational conditions. First, the significantly different behavior of germanium calibration curves (versus silicon) will be discussed. Next, the shape and characteristics of the probe imprints (Ge is softer than Si) and the differences in raw data behavior will be...

High dose ion implantation of heavy elements in Ge induces a rough surface and profile distortions when measured with secondary ion mass spectrometry. In the case of Sb large subsurface holes are also induced by the implantation. The formation of these subsurface structures starts abruptly at a dose between 5∙1014 and 1015at∕cm2. The addition of a SiO2 capping layer on top of Ge prevents the formation of the surface roughness, but has limited impact on the void formation. These voids originate from vacancy clustering during the implant process. Anneal studies show that it is impossible to remove these structures by annealing, limiting the usefulness of high dose Sb implants in Ge for junction formation. In the case of As implantation a similar surface roughness is seen but no void formation. Adding a cap layer removes the surface roughness in this case and improves the secondary ion mass spectroscopy profiles.

The physical bulk properties of metalorganic chemical vapor deposited (MOCVD) deposited HfO 2 layers were characterized as a function of deposition temperature. thickness, and starting surface. It is shown that depositing HfO 2 layers at 300°C results in a lower density film compared to films deposited at higher temperature (e.g., 485 and 600°C). In addition, it is shown that layers deposited at 300°C contain significant amounts of carbon originating from the organic precursor (tetrakis-diethylamidohafnium). As a result of the low density and/or carbon contamination, the dielectric properties of these layers are very poor. It is observed that the density of the film is heavily dependent on the thickness, where very thin layers have a density that is only a fraction of the bulk density regardless of the deposition temperature. For thicker layers, a higher deposition temperature is seen to result in a higher density, although still lower than bulk density, as observed by ellipsometric porosimetry. Finally, the crystalline state of the material is found to be dependent on the deposition temperature, thickness, and post-deposition anneal. Based on our results, MOCVD deposited HfO 2 layers are expected to be polycrystalline and present in its cubic and/or monoclinic phase.

The spreading resistance probe (SRP) and four point probe (FPP) use, respectively, two or four metal probes with loads in the range of 5–100 g to obtain indispensable information on the electrical characteristics (sheet resistance, junction depth, activation degree, profile shape) of impurity depth profiles in silicon. Recently, however, it has been reported that FPP sheet values are becoming irreproducible and that SRP depth profiles can be significantly shallower than the corresponding secondary ion mass spectrometry dopant profiles for ultrashallow structures. In this work we analyze the impact of probe penetration on the accuracy of SRP and FPP measurements for a series of sub-50 nm profiles with different steepness and substrate level. The probe penetration has been measured by atomic force microscopy and ranged from 5 to 130 nm. The FPP sheet resistance errors of up to 300%, as found for the higher loads, can be correlated with the penetration of the probes through the electrical junction taking int...